Decal won't change sizes properly

Hello all,

I have a top down view of a big chunk of land I was trying to add to an assembly of a location. Whenever I try to make the image bigger or smaller it always snaps back to its original size. Is this a limitation with the image being too small, Solidworks, or am I just doing something wrong?

It says to enter a number for the width between 1 and 1640.41994751.

SolidworksPhotoview 360